In a noise canceling headphone, a microphone that collects external noise is disposed in a part of a housing, a signal (canceling signal) that cancels the external noise is generated in response to the external noise collected by the microphone, a speaker unit is driven in response to the generated canceling signal to output a canceling sound, and the external noise is canceled by the canceling sound.
In a feed-forward noise canceling headphone, a microphone that collects external noise is disposed outside a front air chamber. Since a sound output from a speaker unit (a reproduced sound such as a musical sound and a canceling sound) is not fed back by the microphone, the canceling sound does not adversely influence frequency characteristics during use for playing music. Accordingly, the feed-forward noise canceling headphone is suitable for reproducing a high quality-musical sound. The above-mentioned “front air chamber” indicates a space surrounded by an ear pad and covered by the side of a user's head to communicate with an ear canal when the headphone is in use.
Noise canceling headphones having various shapes are known. Included are noise canceling headphones of an on-ear type (supra-concha type) and an ear-muff type (circum-aural type) except for an earplug type (canal type) each of which has a sound-wave introducing part of the microphone facing an external space of a housing of the headphone. Since the sound-wave introducing part of the microphone, therefore, tends to be directly subjected to wind and rain under a high-wind condition and a rainfall condition, noise caused by the above-explained situation is collected too highly to cancel the noise. Depending on a positional relationship between a noise source and the microphone, the noise may reach the user's ears through a housing before reaching the microphone. In that case, the noise to be canceled is heard before outputting a canceling sound, and thereby a canceling effect cannot be expected. Furthermore, there is concern that the canceling sound may accentuate the noise.
A noise canceling headphone for solving the above-described problems is known which effectively cancels noise without depending on the direction of a noise source by uniformly arranging a plurality of microphones on the circumference of an ear cup as a part of a housing. In addition, a noise canceling headphone is known which is designed so that a microphone disposed in a front air chamber collects noise that reaches the user's ears through a housing before being collected by an external microphone, and then a canceling sound that is not affected by the direction of a noise source is output, by combining a feedback system that includes a microphone in a front air chamber with the above-described feed-forward system (See Patent Document 1, for example).    [Patent Document 1] Japanese Unexamined Patent Application No. 2008-116782